Q. I have a sick oak tree in our backyard. It is an older
tree and but not growing well. Our gardener suggested hiring an arborist to
treat the tree and help it recover. Can we purchase something to correct this? Would
an arborist be able to save it? Your thoughts.
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| Sick Oak tree trunk in the backyard. ‘Heritage’ live oak is a good tree choice for two-story homes in Las Vegas. |
A. From the picture you sent it looks like a southern live
oak such as ‘Heritage’. It looks like the trunk of the tree is slow to recover
and has some pretty old wounds. Getting it to recover depends on how far “gone”
it is. You will not know that until the summer hits. Even though it’s a 30 to 40 foot tree (size-wise think of it as a bit larger than European olive). This particular oak is classified in between xeric and mesic and a native to southern Texas and into the Chihuahuan desert. It does well where there is a bit more water and also into the drier locations. The “cons” of this tree
All oaks
like amended soil and don’t like the soil “mineralized” by rock
mulch over time. Rake the rock back three feet from the trunk. Change this area
over to a layer of organics that can rot on top of the soil. Add a thin layer
of finely screened compost to the soil. Water the tree two feet deep once a
week right now. This can be done with a sprinkler on the end of a hose. This
may be increased to twice a week if it gets hot and windy.
Oaks in
general dont like rock up to the trunk but prefer growing in soils getting
organics periodically. Rocks cause the soil to become “mineralized” over time
(organics in the soil are lost to decomposition). This is the reason for adding
compost and wood chips to the top of the soil.
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| Tree roots require deeper irrigation. The bigger the plant, the deeper the roots. Use a length of rebar to judge how to deep to water. To get water deeper with the same amount of time, add more drip emitters! |
Secondly,
this tree needs additional water each time its irrigated; 15 to 20 gallons during
the first few years but now may be 30 to 40 gallons each time. Instead of
increasing or decreasing the minutes, add more and larger drip emitters to the
area under the tree. Put sprinkler hose water into a 6 to 8 foot wide area
under the tree for about one hour and encourage the roots to “chase” the water
into this newly wetted area. This will increase the trees vigor and cause it to
heal fast. No need for additional fertilizer if the compost is rich with
nutrients.
If you
see evidence of borer activity from previous years, it probably was reinfested
each year since that time. Soil drench the area under the tree with a borer
systemic insecticide. Apply it as a soil drench after the tree finishes flowering.